1. Field of the Invention
The present invention relates to a biological composite and a method for reducing H2S.
2. Description of Related Art
Biogas from a wastewater treatment plant is classified as a cheap and environmentally friendly renewable energy, and can be applied as a source of alternative vehicle fuel or in generation of heat, electricity, and chemical compounds. Generally, such biogas contains 65% methane, 30% CO2, 4% N2, 0.2% H2S, and other minor gases. Notably, H2S is found in production of biogas and natural gas, or in the process of papermaking or oil-refining. When the accumulation of H2S reaches a concentration up to 1000 ppm or more, it causes serious erosion to machines such as dynamos, and can be lethal to humans. Therefore, there is a need to reduce H2S as much as possible in relevant processes.
Currently, methods for removing gaseous H2S are mainly physical methods; incineration, Claus process, chemical washing; as well as biological methods. Except for biological methods, the others require high costs due to replacement of consumable materials or setting up of equipment. However, even in biological methods, there are still limitations in the treatment of H2S up to 1000 ppm or more, depending on oxidative activity of different microbes to H2S. Besides, when H2S is oxidized into H2SO4 by microbes, H2SO4 is accumulated and makes the environmental pH value decrease. Accordingly, the growth and activity of the microbes are undesirably influenced, thereby resulting in decreased removal of H2S.
Therefore, there is a need to find a microbe with extremely strong capacity for H2S oxidation. Even if the environmental pH value is decreased, the microbe should be able to retain good oxidative activity to H2S and thus it is advantageous to promote the environmental control development efforts within the papermaking and oil-refining industries as well as in the production of biogas and natural gas.